The quick fix is just fill the cracks with drywall compound, let dry and paint. You might need to sand a little prior to painting, depending on how good you mud the cracks.

The more correct solution would be to tape some adhesive-backed fiberglass tape over the cracks, and skim drywall compound over that. You would have to be fairly handy with drywall compound to get this to look right, or have a fresh supply of sandpaper ready after it dries. The screen-type sandpaper for drywall is great. Turn fans and forced-air system off when sanding. A good vaccuum cleaner when all is said and done.

If you are not that drywall savvy, and you have the cash, you might want to consider having a drywall contractor do the job.